1. Field of the Invention
The present invention relates to a transporter vehicle which is suitably used in transporting such as crushed stones or earth and sand excavated from such as an open-pit stope, a mine, or the like.
2. Description of Prior Art
In general, a large-size transporter vehicle called a dump truck has a tiltable vessel (loading platform) on a frame of a vehicle body, and transports objects to be transported such as crushed stones or earth and sand or the like to an unloading site of, for instance, an exit port or the like in a state in which the objects to be transported are loaded in a large quantity on the vessel.
A transporter vehicle of this type according to the prior art is comprised of a frame extending in the forward and rearward direction; a loading platform which is tiltably provided on a rear portion of the frame so as to load the objects to be transported; an engine which is mounted on the frame by being positioned on the front side of the loading platform; and a cab which is provided on the frame by being positioned above the engine and defines an operator's room in its interior (e.g., see Japanese Patent Laid-Open No. H1-244933).
The frame which is used in such a transporter vehicle is formed by a base frame on a rear side of which the loading platform is provided and on a longitudinally intermediate portion of which left and right column portions projecting upward are formed with the engine sandwiched therebetween, and an upper cross beam provided on the base frame by means of the left and right column portions and adapted to support at least a portion (rear side) of the cab from below.
In this case, the upper cross beam extends in such a manner as to jut out in the leftward and rightward direction so as to be perpendicular to the base frame extending in the forward and rearward direction, and is fixed to each column portion of the base frame by use of a welding means so as to form an integral structure. Consequently, the column portions and the upper cross beam of the base frame form so-called a gate type structure when viewed from the front side, and are formed as a rigid frame structure.
For this reason, the cab provided on the upper cross beam is able to satisfy the rollover protection structure (abbreviated as ROPS) in accordance with ISO and JIS to thereby ensure the safety of the operator or the like who has climbed up into the cab.
By the way, in the above-described transporter vehicle according to the prior art, the upper cross beam for supporting the rear side of the cab from below is integrally formed on the column portions of the base frame by use of a welding means. Therefore, for example, at the time of mounting or dismounting the engine to or from the base frame, the upper cross beam constitutes a hindrance, and the following problem occurs.
Namely, since the engine serving as a prime mover of the transporter vehicle is mounted on the base frame by being positioned on the front side of the loading platform, the engine is unfavorably disposed such that the left and right sides are sandwiched between the left and right column portions of the base frame, and the upper side is covered by the upper cross beam. It should be noted that the engine is an expensive product (part), and if the upper cross beam is welded after mounting the engine on the base frame, there is a possibility of the engine becoming damaged by sparks and the like during welding.
Consequently, when the engine is mounted to the base frame with the upper cross beam integrally formed thereon in, for example, an assembly process of the vehicle, it is necessary to hoist the engine by a crane or the like and lower it into the base frame so as to avoid the upper cross beam while the suspended engine is being transferred in the horizontal direction between the left and right column portions. Thus, a time-consuming operation is required.
Moreover, in case the engine is collided against a peripheral member (e.g., each column portion and the upper cross beam of the base frame), the expensive parts including the engine may become damaged or broken, so that a cautious operation is required for assembly personnel at the time of the carrying in and mounting of the engine. Hence, there is a problem in that the burden imposed on the assembly personnel is large. Additionally, in this respect, a similar problem occurs when the engine is dismounted from the base frame at the time of maintenance such as a periodic inspection.
In addition, when the engine is lifted up (suspended) between the base frame and the upper cross beam, it is necessary to secure a space (vertical gap) for this purpose, so that the upper cross beam must be installed in advance at a higher position than the upper end of the engine with leeway (gap). For this reason, the position of installation height of the cab becomes excessively high, which constitutes a major obstacle in lowering the overall height of the transporter vehicle.
Further, in view of such as the limitation of the transport width, the operation of integrating the upper cross beam to the column portions of the base frame by use of a welding means is normally performed in the field where the transporter vehicle is operated. However, such welding operation in the field consumes extra labor and time. Furthermore, some welding operations require expertise, so that there is a problem in that it is difficult to ensure reliability of welded portions.